panvk: fix sample position when sample shading is disabled
Fixes dEQP-VK.draw.dynamic_rendering.primary_cmd_buff.linear_interpolation.*
when combined with !32127 (merged). On vulkan, gl_FragCoord
is lowered to the pixel coord + sample pos by nir_lower_wpos_center
. The sample position bug then meant that gl_FragCoord
was the position of the first sample rather than the center of the pixel when multisample is enabled but sample shading is not.
I went a long ways down the path of passing the actual raw sample ID through to NIR, so that we could use the original pan_positions[32]
design, but switched to this simpler option once I realized it wasn't necessary.
Fixes panfrost/mesa#26 (closed).